Nonproliferation of nuclear threats is a critical objective in the war against nuclear terrorism. Proactively identifying and interdicting transport of commodities associated with illicit nuclear materials and nuclear weapons can help ensure effective nuclear nonproliferation.
Radioactive atoms are typically characterized for having a high atomic number Z (e.g., plutonium, having an atomic number Z of 94, and uranium, having an atomic number Z of 92). These radioactive atoms are unstable and give off various types of radiations, including gamma rays and neutrons. Gamma-ray spectrum analysis and neutron detectors, based on helium-3 gas, can be employed to detect nuclear radiological materials made out of radioactive atoms. Unfortunately, the signatures of these radiological materials can be diminished by enclosing them in a container made of other non-radiological, high Z number materials, such as lead (having an atomic number Z of 82). Such a container can hinder detection of the radiological materials by masking the signatures of radioactive atoms that are held within the container.